This invention relates to a heat-sensitive recording material which is superior in each of water resistance, printability and recording runnability.
There has been known heat-sensitive recording materials utilizing the color forming reaction between a color former and a color developer, in which the two color forming materials are thermally contacted each other to produce recorded images. These heat-sensitive recording materials are comparatively inexpensive and can be used on a recording equipment which is compact and requires fairly easy maintenance. Because of these advantages, the heat-sensitive recording materials have been used not only as the recording medium of facsimiles and various computers, but also in the other various fields.
As the applications, recording medium for a portable printer, a label or tag printer becomes noticeable accompanied with increased point-of-sales systemalization of retail stores. The handy terminal or the like is often used out of doors. It is a problem that the recording layer easily peels by wetting with rain. Further, since an offset printing must be applied on the recording surface in such an application, a heat-sensitive recording material superior in the printability has been required.
In order to improve the water resistance of a heat-sensitive recording layer, there have been known adding water-proof agents in the heat-sensitive recording layer as shown in Japanese Laid-Open Patent Publications No.36343 of 1962 and No. 33352 of 1969 and using a hydrophobic polymer emulsion as a binder in the heat-sensitive recording layer as shown in Japanese Laid-Open Patent Publications No. 14998 of 1972, No. 18520 of 1972 and No. 8084 of 1990. However, a heat-sensitive recording layer superior in each of water resistance, printability and recording runnability has not been practically obtained.
Further, it has been known to form on the heat-sensitive recording layer a protective layer comprising a water-soluble polymer to dissolve such a problem that recorded images disappear by contacting with an oily finger, handcream, plasticizer comprised in vinyl chloride resins or the like. Although the formation of protective layer effectively prevents sticking, smudges adhered on a thermal head, contamination by rubbing and the like, a heat-sensitive recording material superior in water-resistance and printability can not be obtained.
Therefore, an object of the invention is to dissolve the above problems to provide a heat-sensitive recording material superior in water-resistance and printability and also recording runnability.